Imaging Science Lecture 1.docx

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Medical Biophysics
Medical Biophysics 3503G
James Lacefield

3503 Imaging Science Lecture 1 January 9 th Screening Mammography Policy • It is important for women to get screened for breast cancer every year once they reach a certain age. o Screening: A diagnostic test performed in a large number of apparently healthy subjects to detect occult (hidden) disease in a small fraction of those subjects  Imaging people for breast cancer who currently do NOT have any symptoms • Standard is annual exams ages 40-70. In 2009 a task force in US that is responsible for making recommendations about how health care resources are used came out with new guidelines: in 2011, equivalent Canadian task force endorsed those guidelines: o Biennial exams for ages 50-74 o Biennial exams by individual decision at ages 40-49 o New recommendations is women should go for mammograms less o Biennial means every two years (Biannual is twice a year) • False positives did not cause the change in recommendations. The reason the recommendations were changed to less screening than before has to do with concerns about overdiagnosis: Detection of pre-malignant tumours that would not have produced symptoms during the patient’s lifetime if left untreated o If a tumour is detected, it may be benign or malignant o Malignant lesions can metastasize and kill you if not treated. Benign lesions just sit there and don’t cause any problems unless they get so big that they are crushing important body parts. There is a subset of benign lesions, Pre-malignant, that have the chance of transforming into malignant lesions and becoming aggressive in the future. o There is currently no test to tell if a Pre-malignant lesion will transform or not. Standard of care is all of the women who have pre-malignant lesions detected get therapy (Surgery, radiation, chemotherapy). Some of the patients are sent for this aggressive therapy when, if they had been left alone, the tumour wouldn’t have done anything. So they risk the side effects of treatment for no benefit. This is referred to as overtreatment: treatment that is more aggressive than what you really need. Granting Agency Debate • Any grant applications that were specific to trying to develop improvements in the technology for screening for breast cancer should go directly into the garbage because even if the physics and engineering behind it worked out it would not help patients. Therefore the funding agency shouldn’t fund anything that wouldn’t actually help its patients. Imaging Science • A multidisciplinary field concerned with the generation, collection, duplication, analysis, modification, and visualization of images • The foundation of imaging science as a discipline is the “imaging chain”, a conceptual model describing all of the factors that must be considered when developing a system for creating images • A way to assess the quality of an image and it’s a set of tools to assess whether the information provided by the image is effective for a specific purpose. The tools of imaging science are agnostic about the physics of how the image was formed and are agnostic about the instrumentation that was used to acquire the image and so forth. The tools of imaging science actually focus on the information that’s in the image after it’s been acquired and displayed to the radiologist. They are applicable to any kind of imaging (medical or nonmedical). • What is an Image? o A measurement made as a function of position (and possibly time) presented in
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